Communication systems are known to include a central controller, a plurality of communication units, and communication resources. In such systems, the communication resources may be RF frequencies, pairs of RF frequencies, TDM slots, or any medium to carry RF transmissions.
In a secure communication system, communications are transmitted over communication resources in an encrypted manner. A message is typically encrypted using a particular encryption algorithm, or technique, along with an encryption key that adds extra security into secure transmissions. Examples of encryption algorithms include data encryption standard (DES), digital voice protection (DVP), cipher feedback, and open loop feedback. These encryption algorithms are generally used throughout the secure technology arena.
In secure communication systems, a communication unit has the option of utilizing the security of encrypted transmissions, or transmitting in an unencrypted, or clear, mode. Thus, the central controller, or communication resource allocator, must be equipped to process both clear communication requests and encrypted communication requests. Most users of a secure communication system, however, transmit in an encrypted mode.
Because the secure communication system can handle both clear and encrypted communications, it is possible for an unauthorized communication unit to operate on the secure communication system in a clear mode and go undetected. When unauthorized communication units are accessing a communication system, whether a secure or a non-secure system, the efficiency of such systems decreases. Thus, authorized users suffer in slower throughput of their communication requests as a result of unauthorized use of the system.
Present technologies do little to detect unauthorized use of a secure communication system, while a substantial amount of technological effort is placed into ensuring that secure communications remain secure. Therefore, a need exists for a method of detecting unauthorized use of a secure communication system.